Airworthiness Directive · Amendment 39-18574 · Fuselage
The Boeing Company Airplanes
Superseded. A later AD replaced this one: AD 2016-16-13. Comply with the one in force.
(1) This AD applies to The Boeing Company Model 737-300, -400, and -500 series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015.
(2) Installation of Supplemental Type Certificate (STC) ST01219SE (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgstc.nsf/0/BE866B732F6CF31086257B9700692796?OpenDocument&Highlight=st01219se) does not affect the ability to accomplish the actions required by this AD. Therefore, for airplanes on which STC ST01219SE is installed, a “change in product” alternative method of compliance (AMOC) approval request is not necessary to comply with the requirements of 14 CFR 39.17.
We are superseding Airworthiness Directive (AD) 2012-12-04, for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. AD 2012-12-04 required repetitive external detailed inspections and nondestructive inspections to detect cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between station (STA) 400 and STA 460, and repair if necessary. This new AD requires a preventive modification of the fuselage skin at crown stringers S-1 and S-2R. This new AD also reduces the inspection threshold for certain airplanes. This AD was prompted by a determination that, for certain airplanes, the skin pockets adjacent to the Air Traffic Control (ATC) antenna are susceptible to widespread fatigue damage. We are issuing this AD to detect and correct fatigue cracking of the fuselage skin panels at the chem-mill steps, which could result in sudden fracture and failure of the fuselage skin panels, and consequent rapid decompression of the airplane.
At the applicable time specified in tables 1, 2, 3, and 5 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015, except as required by paragraphs (l)(1) and (l)(2) of this AD: Do the actions specified in paragraphs (g)(1) and (g)(2) of this AD, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015, except as required by paragraph (l)(3) of this AD. Repeat the applicable inspections thereafter at the applicable times specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015.
(1) Do an external detailed inspection for cracking of the fuselage skin chem-mill steps.
(2) Do an external non-destructive (medium frequency eddy current, magneto optical imaging, C-Scan, or ultrasonic phased array) inspection for cracking of the fuselage skin chem-mill steps.
If any cracking is found during any inspection required by paragraph (g) of this AD, do the applicable actions specified in paragraph (h)(1), (h)(2), or (h)(3) of this AD.
(1) Repair before further flight in accordance with Part 2 (for Group 1 airplanes) or Part 7 (for Group 2 airplanes) of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015; except as required by paragraph (l)(3) of this AD. Installation of a repair that meets the conditions specified in Note (a) of table 1, 2, 3, or 5 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015, terminates the repetitive inspections required by paragraph (g) of this AD for the area covered by that repair only.
(2) For Group 1 airplanes: Accomplishing the modification specified in paragraph (i) of this AD is a method of compliance with paragraph (h)(1) of this AD.
(3) If any cracking is found in any area not covered by the preventive modification doubler during any inspection required by paragraph (g) of this AD: Repair before further flight, in accordance with Part 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015, except as provided by paragraph (n)(4) of this AD. Both new and existing repairs are allowed if the repair covers all eight chem-mill step inspection areas between STA 410 and STA 450, and the repairs were done using a method approved in accordance with the procedures specified in paragraph (n)(1) of this AD.
For Group 1 airplanes: At the applicable time specified in tables 1, 2 and 3 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015, except as required by paragraphs (l)(1) and (l)(2) of this AD, do a preventive modification of the fuselage skin at crown stringers S-1 and S-2R, including all applicable related investigative actions in accordance with Part 9 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015, except as provided by paragraph (n)(4) of this AD. Do all applicable related investigative actions concurrently with the modification. Installation of a preventive modification terminates the repetitive inspections required by paragraph (g) of this AD for the modified area only. Thereafter, repeat the inspections specified in Part 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015.
Accomplishing a modification of the chem-mill steps at any location identified in Boeing Service Bulletin 737-53A1293, Revision 2, dated August 10, 2011, using a method approved in accordance with the procedures specified in paragraph (n)(1) of this AD, terminates the repetitive inspections required by paragraph (g) of this AD for the modified area only.
Tables 4 and 6 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015, specify post-repair/post-modification airworthiness limitation inspections in compliance with 14 CFR 25.571(a)(3) at the modified locations, which support compliance with 14 CFR 121.1109(c)(2) or 129.109(b)(2). As airworthiness limitations, these inspections are required by maintenance and operational rules. It is therefore unnecessary to mandate them in this AD. Deviations from these inspections require FAA approval, but do not require an alternative method of compliance.
(1) Where Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015, specifies a compliance time “after the Revision 3 date of this service bulletin,” this AD requires compliance within the specified compliance time after the effective date of this AD.
(2) Where the Condition column of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015, specifies a condition based on when an airplane has or has not been inspected, this AD bases the condition on whether an airplane has or has not been inspected on the effective date of this AD.
(3) Where Boeing Alert Service Bulletin 737-53A1293, Revision 3, dated January 23, 2015, specifies to contact Boeing for repair or preventive modification instructions: Before further flight, do the repair or preventive modification, as applicable, using a method approved in accordance with the procedures specified in paragraph (n)(1) of this AD.
